here is a list of SoCal skateparks in general. I don't know which ones allow bikes, but at least it's list to see what's around you and you can find out about bikes by calling the ones you're interested in:

here is a list of SoCal skateparks in general. I don't know which ones allow bikes, but at least it's list to see what's around you and you can find out about bikes by calling the ones you're interested in: